1. Field of the Invention
This invention concerns ultraviolet illumination equipment to for dry washing by ultraviolet radiation from a dielectric-barrier discharge lamp, and by ozone created at the same time by the ultraviolet radiation.
2. Description of the Related Art
Technology for dry washing by means of ultraviolet illumination equipment using an ultraviolet radiation light source has been known for some time. Such ultraviolet illumination equipment has been used for light washing and precision light washing in the liquid crystal and semiconductor field.
Ultraviolet illumination equipment of this type have previously used, as the ultraviolet light source, low-pressure mercury lamps and medium pressure mercury lamps that radiate well at the ultraviolet wavelengths of 253.7 nm or 184.9 nm.
Various chemicals such as organic solvents, acids and alkalis are used when processing semiconductor or liquid crystal devices, and so these chemicals are often removed by evaporation. Among these chemicals are those that absorb ultraviolet radiation and are broken down by the energy and produce reaction products after reacting with other chemicals. For example, ammonium bisulfate (NH4)H(SO4)2 and ammonium sulfate (NH4)2SO4 are produced.
Such reaction products circulate as fine dust particles within the clean room, and when these fine dust particles accumulate, they sometimes become a factor with a deleterious effect on the manufacturing process.
On the other hand, in recent years, dielectric-barrier discharge lamps with high energy a single wavelength and good efficiency have come to be used, as the ultraviolet illumination equipment in place of the mercury lamps described above.
In ultraviolet illumination equipment that uses a dielectric-barrier discharge lamp as the ultraviolet light source, the dielectric-barrier discharge lamp is placed in a receptacle that is sealed to separate it from the atmosphere, and the ultraviolet radiation emitted by the dielectric-barrier discharge lamp passes through a part of that receptacle to illuminate the item to be processed.
Nevertheless, there has been a problem in that ultraviolet illumination equipment that uses a dielectric-barrier discharge lamp has a window through which the ultraviolet radiation passes, and the reaction products mentioned above are carried by convection and adhere to this window.
The reason the reaction products adhere to the window is that when the dielectric-barrier discharge lamp is lit, the temperature of the front of the lamp is low, about 70xc2x0 C., and so the radiant heat radiated from the lamp cannot heat the window sufficiently. Because of that, reaction products that come into contact with the window are not carried away from the window by the radiant heat, but immediately adhere to the window.
As a result, there are the problems in that the transparency to ultraviolet radiation is lowered by the reaction products that adhere to the window, and the intensity of the ultraviolet radiation is not uniform throughout the area of illumination.
There is the further in that processing defects and flaws appear on the item being processed, and the yield is reduced.
In cases of a considerable buildup of reaction products adhered to the window, there is a problem in that the reaction products can peel off the window as large pieces of debris, and contaminate the processing environment of the clean room.
This invention was made on the basis of the situation described above. Its primary purpose is to provide ultraviolet illumination equipment that makes it possible to prevent reaction products due to ultraviolet radiation from adhering to the window, and thus to prevent reduction of the intensity of the ultraviolet radiation and the formation of debris from the reaction products.
In order to resolve the problems described above, the ultraviolet illumination equipment has a dielectric-barrier discharge lamp located within a receptacle, a window in the receptacle through which the ultraviolet radiation from the dielectric-barrier discharge lamp is emitted, and a heating means to heat the window to at least 100xc2x0 C.
In another embodiment of the ultraviolet illumination equipment in accordance with the present invention, the heating means is established within the ultraviolet illumination equipment.
In another embodiment of the ultraviolet illumination equipment in accordance with the present invention, the heating means is a thick-film heater formed on the surface of the window.
In another embodiment of the ultraviolet illumination equipment in accordance with the present invention, the heating means is a linear beater formed on the surface of the window.
In another embodiment of the ultraviolet illumination equipment in accordance with the present invention, a the heating means is an incandescent bulb.